VulnerabilityPublished 13 Apr 2026Updated 5 Nov 2026

CVE-2026-31427: Linux kernel · netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6 : update Linux kernel when convenient.

Data as of 5 Nov 2026, 22:04 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-05.

Patch

Available – fixed in fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6, faa6ea32797a1847790514ff0da1be1d09771580, 82baeb871e8f04906bc886273fdf0209e1754eb3 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6	Fixed in fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < faa6ea32797a1847790514ff0da1be1d09771580	Fixed in faa6ea32797a1847790514ff0da1be1d09771580
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < 82baeb871e8f04906bc886273fdf0209e1754eb3	Fixed in 82baeb871e8f04906bc886273fdf0209e1754eb3
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < 52fdda318ef2362fc5936385bcb8b3d0328ee629	Fixed in 52fdda318ef2362fc5936385bcb8b3d0328ee629
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < 7edca70751b9bdb5b83eed53cde21eccf3c86147	Fixed in 7edca70751b9bdb5b83eed53cde21eccf3c86147
LinuxLinux	Affected ≥ 4ab9e64e5e3c0516577818804aaf13a630d67bc9, < 6e5e3c87b7e6212f1d8414fc2e4d158b01e12025	Fixed in 6e5e3c87b7e6212f1d8414fc2e4d158b01e12025

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp process_sdp() declares union nf_inet_addr rtp_addr on the stack and passes it to the nf_nat_sip sdp_session hook after walking the SDP media descriptions. However rtp_addr is only initialized inside the media loop when a recognized media type with a non-zero port is found. If the SDP body contains no m= lines, only inactive media sections (m=audio 0 ...) or only unrecognized media types, rtp_addr is never assigned. Despite that, the function still calls hooks->sdp_session() with &rtp_addr, causing nf_nat_sdp_session() to format the stale stack value as an IP address and rewrite the SDP session owner and connection lines with it. With CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this results in the session-level o= and c= addresses being rewritten to 0.0.0.0 for inactive SDP sessions. Without stack auto-init the rewritten address is whatever happened to be on the stack. Fix this by pre-initializing rtp_addr from the session-level connection address (caddr) when available, and tracking via a have_rtp_addr flag whether any valid address was established. Skip the sdp_session hook entirely when no valid address exists.

References

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