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NVD / CVE Program· CNA Linux

CVE-2026-23457: netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()

HighCVSS 8.6 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 34/100)

  • 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: 0.45% (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 528b4509c9dfc272e2e92d811915e5211650d383, 75fcaee5170e7dbbee778927134ef2e9568b4659, 865dba58958c3a86786f89a501971ab0e3ec6ba9.

Low priority for now. Upgrade to Linux Linux 528b4509c9dfc272e2e92d811915e5211650d383, 75fcaee5170e7dbbee778927134ef2e9568b4659, 865dba58958c3a86786f89a501971ab0e3ec6ba9 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: netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp() sip_help_tcp() parses the SIP Content-Length header with simple_strtoul(), which returns unsigned long, but stores the result in unsigned int clen. On 64-bit systems, values exceeding UINT_MAX are silently truncated before computing the SIP message boundary. For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32, causing the parser to miscalculate where the current message ends. The loop then treats trailing data in the TCP segment as a second SIP message and processes it through the SDP parser. Fix this by changing clen to unsigned long to match the return type of simple_strtoul(), and reject Content-Length values that exceed the remaining TCP payload length.

Published
Apr 3, 2026
Updated
Nov 10, 2026
EPSS
0.4% · 39th percentile

Report tools

JSON

Action score

34

Monitor

Low priority for now.

CVSS
34 / 40 · 8.6 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
8.6
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
  • No public exploit code on record
  • A fix has been released

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Follow CVE-2026-23457

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
linuxlinux kernel

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

    • 2.6.34affected
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before ed81b6a7012485acdb9c6c80735a0b7d8e5e1873affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before cd1b7403ec835f8a0b3f1f7e68ac26af2cb1e42faffected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before b75209debb9adab287b3caa982f77788c1e15027affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before 528b4509c9dfc272e2e92d811915e5211650d383affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before 75fcaee5170e7dbbee778927134ef2e9568b4659affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before 865dba58958c3a86786f89a501971ab0e3ec6ba9affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before d4f17256544cc37f6534a14a27a9dec3540c2015affected · git
    • f5b321bd37fbec9188feb1f721ab46a5ac0b35da and later · before fbce58e719a17aa215c724473fd5baaa4a8dc57caffected · git
    • before 2.6.34not affected · semver
Affected versions · NVD (8)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.34 and later · before 5.10.253
  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 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 kernel7.0

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.10-16.19.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • 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…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-23455Apr 3, 2026 · netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
    36Monitor
  • ← EarlierCVE-2026-23456Apr 3, 2026 · netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case
    32Monitor
  • Later →CVE-2026-23458Apr 3, 2026 · netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct()
    31Monitor

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 Linux528b4509c9dfc272e2e92d811915e5211650d383Vendor (CNA)
Linux Linux75fcaee5170e7dbbee778927134ef2e9568b4659Vendor (CNA)
Linux Linux865dba58958c3a86786f89a501971ab0e3ec6ba9Vendor (CNA)
Linux Linuxb75209debb9adab287b3caa982f77788c1e15027Vendor (CNA)
Linux Linuxcd1b7403ec835f8a0b3f1f7e68ac26af2cb1e42fVendor (CNA)
Linux Linuxd4f17256544cc37f6534a14a27a9dec3540c2015Vendor (CNA)
Linux Linuxed81b6a7012485acdb9c6c80735a0b7d8e5e1873Vendor (CNA)
Linux Linuxfbce58e719a17aa215c724473fd5baaa4a8dc57cVendor (CNA)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)

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.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-3163321 days apartrxrpc: Fix integer overflow in rxgk_verify_response()
    39Monitor
  • CVE-2026-3164921 days apartnet: stmmac: fix integer underflow in chain mode
    39Monitor
  • CVE-2026-3165921 days apartbatman-adv: reject oversized global TT response buffers
    39Monitor
  • CVE-2026-4334135 days apartnet/ipv6: ioam6: prevent schema length wraparound in trace fill
    39Monitor
  • CVE-2026-4603954 days apartrxgk: Fix potential integer overflow in length check
    39Monitor
  • CVE-2026-4632567 days apartRDMA/rxe: Fix iova-to-va conversion for MR page sizes != PAGE_SIZE
    39Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

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
low · data can be read
Integrity
low · 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
Low
Integrity impact
Low
Availability impact
High

Weakness class (CWE)

CWE-190 · Integer Overflow or Wraparound

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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.

ATT&CK techniques

—

References

Show all references (10 more)

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

All records