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NVD / CVE Program· CNA Linux

CVE-2026-89551: SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow

Noroxi assessment

Priority: Monitor (action score 39/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.51% (FIRST EPSS).
  • 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 3f491306dcb673ff5e78e1044ba450c58978774e, 4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4, 85e9602650e9df07190abe817cee3b4d9bc3df17; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 3f491306dcb673ff5e78e1044ba450c58978774e, 4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4, 85e9602650e9df07190abe817cee3b4d9bc3df17; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 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: SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow xdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by walking the tail, pages, and head iovecs. Each per-section step uses min_t() so it never removes more bytes than that section holds, but the final accounting at the fix_len label subtracts the total bytes actually consumed from buf->len without any clamp: fix_len: buf->len -= (len - trim); When the caller has set buf->len to a value smaller than the sum of the iov_lens, (len - trim) can exceed buf->len and the unsigned subtraction wraps to near UINT_MAX. gss_krb5_unwrap_v2() reaches xdr_buf_trim() in exactly that state: buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip; buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip); xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); buf->len is a small wire-derived value while the iov_lens are at page scale, so the per-section loops legitimately consume far more bytes than buf->len records. The wrapped buf->len then propagates as the authoritative stream bound into every downstream XDR decoder. Fix by clamping the decrement so buf->len bottoms out at zero: buf->len -= min_t(unsigned int, buf->len, len - trim); On the normal path where the iov_lens sum to buf->len, (len - trim) is always <= buf->len and the result is identical to before. No callers change behavior outside the underflow case.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 44th percentile
CWE
—

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

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.

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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.

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Affected 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.

—

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

    • 3.9affected
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before a3d77bcd974b8625d16bddf448cb3a1b5e37049caffected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before fa16bbe987b47e771e52eeb1b4540f18d92496acaffected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before a924ac4c78afab71bf82641afa3b62e0c4a8b55eaffected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before 4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4affected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before e6267cccd7b05cc514e57f2160aa8db85f5c2701affected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before ad0cce80d4af2f74674e8b635d97aa3880e83da8affected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before 85e9602650e9df07190abe817cee3b4d9bc3df17affected · git
    • 4c190e2f913f038c9c91ee63b59cd037260ba353 and later · before 3f491306dcb673ff5e78e1044ba450c58978774eaffected · git
    • before 3.9not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.6-17.2.6-1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_73before 18-2.118-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_75before 16-2.116-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_82before 9-2.19-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_83before 9-2.19-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_84before 7-2.17-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_85before 6-2.16-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_86before 5-2.15-2.1
SUSE:Linux Enterprise Live Patching 12 SP5kgraft-patch-SLE12-SP5_Update_87before 2-2.12-2.1
SUSE:Linux Enterprise Live Patching 15 SP4kernel-livepatch-SLE15-SP4_Update_59before 2-150400.2.12-150400.2.1
SUSE:Linux Enterprise Live Patching 15 SP5kernel-livepatch-SLE15-SP5_Update_31before 19-150500.2.119-150500.2.1
SUSE:Linux Enterprise Live Patching 15 SP5kernel-livepatch-SLE15-SP5_Update_32before 16-150500.2.116-150500.2.1
SUSE:Linux Enterprise Live Patching 15 SP5kernel-livepatch-SLE15-SP5_Update_33before 16-150500.2.116-150500.2.1
SUSE:Linux Enterprise Live Patching 15 SP5kernel-livepatch-SLE15-SP5_Update_35before 15-150500.2.115-150500.2.1
SUSE:Linux Enterprise Live Patching 15 SP6kernel-livepatch-SLE15-SP6_Update_27before 8-150600.2.18-150600.2.1
SUSE:Linux Enterprise Live Patching 15 SP6kernel-livepatch-SLE15-SP6_Update_29before 6-150600.2.16-150600.2.1
SUSE:Linux Enterprise Live Patching 15 SP6kernel-livepatch-SLE15-SP6_Update_30before 5-150600.2.15-150600.2.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_19before 6-150700.2.16-150700.2.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_20before 5-150700.2.15-150700.2.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7_Update_21before 3-150700.2.13-150700.2.1
SUSE:Linux Enterprise Live Patching 15 SP7kernel-livepatch-SLE15-SP7-RT_Update_12before 11-150700.2.111-150700.2.1

+53

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-89549Sep 11, 2026 · sunrpc: route to a populated pool in svc_pool_for_cpu()
    30Monitor
  • ← EarlierCVE-2026-89550Sep 11, 2026 · SUNRPC: svcauth_gss: enforce krb5 token minimum length
    39Monitor
  • Later →CVE-2026-89552Sep 11, 2026 · params: fix charp corruption on allocation failure
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux3f491306dcb673ff5e78e1044ba450c58978774eVendor (CNA)
Linux Linux4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4Vendor (CNA)
Linux Linux85e9602650e9df07190abe817cee3b4d9bc3df17Vendor (CNA)
Linux Linuxa3d77bcd974b8625d16bddf448cb3a1b5e37049cVendor (CNA)
Linux Linuxa924ac4c78afab71bf82641afa3b62e0c4a8b55eVendor (CNA)
Linux Linuxad0cce80d4af2f74674e8b635d97aa3880e83da8Vendor (CNA)
Linux Linuxe6267cccd7b05cc514e57f2160aa8db85f5c2701Vendor (CNA)
Linux Linuxfa16bbe987b47e771e52eeb1b4540f18d92496acVendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · Debian:12Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_1219-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_1812-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_1910-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_219-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_257-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_266-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0_Update_276-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0-RT_Update_239-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0-RT_Update_257-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0-RT_Update_276-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0-RT_Update_285-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-MICRO-6-0-RT_Update_293-1.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:kernel-livepatch-SLE15-SP5_Update_3119-150500.2.1 · SUSE:Linux Enterprise Live Patching 15 SP5Package registry (OSV)
suse:kernel-livepatch-SLE15-SP5_Update_3216-150500.2.1 · SUSE:Linux Enterprise Live Patching 15 SP5Package registry (OSV)
suse:kernel-livepatch-SLE15-SP5_Update_3316-150500.2.1 · SUSE:Linux Enterprise Live Patching 15 SP5Package registry (OSV)
suse:kernel-livepatch-SLE15-SP5_Update_3515-150500.2.1 · SUSE:Linux Enterprise Live Patching 15 SP5Package registry (OSV)
suse:kernel-livepatch-SLE15-SP6_Update_278-150600.2.1 · SUSE:Linux Enterprise Live Patching 15 SP6Package registry (OSV)

+7

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

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.

No dated events beyond publication.

EPSS, last 120 days

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 researchers

Finders, 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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

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)

—

CVSS 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

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records