CVE-2026-23457Network attack vector

SIP traffic disruption via Content-Length truncation

Published Apr 3, 2026 · Updated Apr 3, 2026

Integer truncation in the Linux Kernel SIP conntrack helper allows remote attackers to disrupt SIP gateway traffic using crafted TCP data. sip_help_tcp() stores simple_strtoul()'s unsigned-long Content-Length result in a 32-bit unsigned integer, so oversized values wrap and trailing bytes are reprocessed as another SIP/SDP message. Exposure requires the nf_conntrack_sip helper to be active on a 64-bit firewall, NAT device, or SIP gateway; expectation-state pollution can block calls or media and permit limited otherwise-filtered traffic.

CVSS severity8.6
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer truncation in the Linux Kernel SIP conntrack helper allows remote attackers to disrupt SIP gateway traffic using crafted TCP data. sip_help_tcp() stores simple_strtoul()'s unsigned-long Content-Length result in a 32-bit unsigned integer, so oversized values wrap and trailing bytes are reprocessed as another SIP/SDP message. Exposure requires the nf_conntrack_sip helper to be active on a 64-bit firewall, NAT device, or SIP gateway; expectation-state pollution can block calls or media and permit limited otherwise-filtered traffic.

The record

CVE
CVE-2026-23457
Published
Apr 3, 2026
Updated
Apr 3, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.34
  2. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <528b4509c9dfc272e2e92d811915e5211650d383
  3. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <75fcaee5170e7dbbee778927134ef2e9568b4659
  4. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <865dba58958c3a86786f89a501971ab0e3ec6ba9
  5. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <b75209debb9adab287b3caa982f77788c1e15027
  6. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <d4f17256544cc37f6534a14a27a9dec3540c2015
  7. Affected versionversion=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <fbce58e719a17aa215c724473fd5baaa4a8dc57c

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.34; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <528b4509c9dfc272e2e92d811915e5211650d383; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <75fcaee5170e7dbbee778927134ef2e9568b4659; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <865dba58958c3a86786f89a501971ab0e3ec6ba9; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <b75209debb9adab287b3caa982f77788c1e15027; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <d4f17256544cc37f6534a14a27a9dec3540c2015; version=f5b321bd37fbec9188feb1f721ab46a5ac0b35da <fbce58e719a17aa215c724473fd5baaa4a8dc57c

Published CVSS scores

8.6Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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