CVE-2026-31402: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache
Noroxi assessment
Priority: Monitor (action score 39/100)
- Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
- Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 68% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: Linux Linux 0f0e2a54a31a7f9ad2915db99156114872317388, 2665887a69437a8a4f552f69509eecfb73d4aa19, 5133b61aaf437e5f25b1b396b14242a6bb0508e2.
Low priority for now. Upgrade to Linux Linux 0f0e2a54a31a7f9ad2915db99156114872317388, 2665887a69437a8a4f552f69509eecfb73d4aa19, 5133b61aaf437e5f25b1b396b14242a6bb0508e2 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix heap overflow in NFSv4.0 LOCK replay cache The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request.
- BDU:2026-05258
- ALSA-2026:13565
- ALSA-2026:13566
- ALSA-2026:13577
- ALSA-2026:13578
- ALSA-2026:19568
- ALSA-2026:19569
- RHSA-2026:10108
- RHSA-2026:11313
- RHSA-2026:13565
- RHSA-2026:13566
- RHSA-2026:13577
- RHSA-2026:13578
- RHSA-2026:13664
- RHSA-2026:13681
- RHSA-2026:13734
- RHSA-2026:13936
- RHSA-2026:14137
- RHSA-2026:14165
- RHSA-2026:14301
- Published
- Apr 3, 2026
- Updated
- Oct 19, 2026
- EPSS
- 1.1% · 68th percentile
- CWE
- CWE-787
Report tools
Action score
39
Monitor
Low priority for now.
- CVSS
- 39 / 40 · 9.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 9.8
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- Proof of concept exists, no weaponized module
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel2.6.12.1 and later · before 5.10.253
- linux linux kernel5.11 and later · before 6.1.167
- linux linux kernel6.2 and later · before 6.6.130
- linux linux kernel6.7 and later · before 6.12.78
- linux linux kernel6.13 and later · before 6.18.20
- linux linux kernel6.19 and later · before 6.19.10
- linux linux kernel2.6.12
- linux linux kernel7.0
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 2.6.12affected
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before f9fcb4441f6c02bb20c2eb340101e27dfe23607caffected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 2665887a69437a8a4f552f69509eecfb73d4aa19affected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before c9452c0797c95cf2378170df96cf4f4b3bca7effaffected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 8afb437ea1f70cacb4bbdf11771fb5c4d720b965affected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0affected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 0f0e2a54a31a7f9ad2915db99156114872317388affected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before ae8498337dfdfda71bdd0b807c9a23a126011d76affected · git
- 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 5133b61aaf437e5f25b1b396b14242a6bb0508e2affected · git
- before 2.6.12not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | kernel | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel-matched | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-extra | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel-matched | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-extra | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-abi-stablelists | before 6.12.0-124.55.1.el10_1 | 6.12.0-124.55.1.el10_1 |
| AlmaLinux:10 | kernel-abi-stablelists | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-cross-headers | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-debug | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-debug-core | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel-matched | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
| AlmaLinux:10 | kernel-debug-modules | before 6.12.0-211.16.1.el10_2 | 6.12.0-211.16.1.el10_2 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2026-31396Apr 3, 2026 · net: macb: fix use-after-free access to PTP clock31Monitor
- ← EarlierCVE-2026-31401Apr 3, 2026 · HID: bpf: prevent buffer overflow in hid_hw_request31Monitor
- Later →CVE-2026-31403Apr 3, 2026 · NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 0f0e2a54a31a7f9ad2915db99156114872317388 | Vendor (CNA) |
| Linux Linux | 2665887a69437a8a4f552f69509eecfb73d4aa19 | Vendor (CNA) |
| Linux Linux | 5133b61aaf437e5f25b1b396b14242a6bb0508e2 | Vendor (CNA) |
| Linux Linux | 8afb437ea1f70cacb4bbdf11771fb5c4d720b965 | Vendor (CNA) |
| Linux Linux | ae8498337dfdfda71bdd0b807c9a23a126011d76 | Vendor (CNA) |
| Linux Linux | c9452c0797c95cf2378170df96cf4f4b3bca7eff | Vendor (CNA) |
| Linux Linux | dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0 | Vendor (CNA) |
| Linux Linux | f9fcb4441f6c02bb20c2eb340101e27dfe23607c | Vendor (CNA) |
| almalinux:kernel | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-core | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-core | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel-matched | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-core | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-extra | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-devel | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-devel-matched | 5.14.0-611.54.1.el9_7 · AlmaLinux:9 | Package registry (OSV) |
| debian:linux | 6.1.170-1 · Debian:12 | Package registry (OSV) |
| red hat:bpftool-debuginfo | 0:7.3.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-debuginfo | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel-matched | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-debuginfo | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel-matched | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-debug-debuginfo | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
| red hat:kernel-debug-devel | 0:5.14.0-427.121.1.el9_4 · Red Hat:rhel_eus:9.4::appstream | Package registry (OSV) |
+17
Exploit status
Proof of concept available
A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.
Evidence
- Proof-of-concept repository on GitHub ×1
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Proof-of-concept repository on GitHub | stars:0 | 2026-04-09 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- First PoC+5 d
- TodayOct 29, 2026+209 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (19 more)Show less
- access.redhat.com/errata/RHSA-2026:13566
- access.redhat.com/errata/RHSA-2026:13577
- access.redhat.com/errata/RHSA-2026:13578
- access.redhat.com/errata/RHSA-2026:13664
- git.kernel.org/stable/c/0f0e2a54a31a7f9ad2915db99156114872317388
- git.kernel.org/stable/c/2665887a69437a8a4f552f69509eecfb73d4aa19
- git.kernel.org/stable/c/5133b61aaf437e5f25b1b396b14242a6bb0508e2
- git.kernel.org/stable/c/8afb437ea1f70cacb4bbdf11771fb5c4d720b965
- git.kernel.org/stable/c/ae8498337dfdfda71bdd0b807c9a23a126011d76
- git.kernel.org/stable/c/c9452c0797c95cf2378170df96cf4f4b3bca7eff
- git.kernel.org/stable/c/dad0c3c0a8e5d1d6eb0fc455694ce3e25e6c57d0
- git.kernel.org/stable/c/f9fcb4441f6c02bb20c2eb340101e27dfe23607c
- access.redhat.com/errata/RHSA-2026:10108
- access.redhat.com/errata/RHSA-2026:11313
- access.redhat.com/errata/RHSA-2026:13681
- access.redhat.com/errata/RHSA-2026:13734
- access.redhat.com/errata/RHSA-2026:13936
- access.redhat.com/errata/RHSA-2026:14137
- access.redhat.com/errata/RHSA-2026:14165
Vendor advisories and official records. Exploit/PoC links are deliberately left out.