Skip to content
VulniPulse
Sign in
Advisory severityMediumRed Hat Linux

Medium [CVE-2026-53240] fix use-after-free on first_skb in __input_process_payload

This medium-severity Red Hat Linux advisory covers CVE-2026-53240.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-53240 Source published Source updated

VulniPulse record published Record updated

CVE-2026-53240
Affected products & platforms
Red Hat LinuxUnclassified
Open source advisory

Summary

In the Linux kernel, the following vulnerability has been resolved: xfrm: iptfs: fix use-after-free on first_skb in __input_process_payload __input_process_payload() stores first_skb into xtfs->ra_newskb under drop_lock when starting partial reassembly, then unlocks and breaks out of the processing loop.

The post-loop check reads xtfs->ra_newskb without the lock to decide whether first_skb is still owned: if (first_skb && first_iplen &&!defer && first_skb!= xtfs->ra_newskb) Between spin_unlock and this read, a concurrent CPU running iptfs_reassem_cont() (or the drop_timer hrtimer) can complete reassembly, NULL xtfs->ra_newskb, and free the skb.

The check then evaluates first_skb!= NULL as true, and pskb_trim/ip_summed/consume_skb operate on the freed skb — a use-after-free in skbuff_head_cache. Replace the unlocked read with a local bool that records whether first_skb was handed to the reassembly state in the current call.

The flag is set after the existing spin_unlock, before the break, using the pointer equality that is stable at that point (first_skb == skb iff first_skb was stored in ra_newskb). A race condition during partial packet reassembly in the __input_process_payload() function can lead to a use-after-free vulnerability.

This occurs when a concurrent process frees a packet buffer (skb) before it is checked, allowing subsequent operations to access freed memory.

Is CVE-2026-53240 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-53240 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-53240?

The advisory VulniPulse tracks names no fixed release. Follow Red Hat's guidance for workarounds and updates.

Confirm against the vendor advisory before you patch.

Affected versions

No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.

Official advisory · medium-confidence parse· fetched 15 days ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.

Official advisory · medium-confidence parse· fetched 15 days ago·verify at source

Mitigation

The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.

Official advisory · medium-confidence parse· fetched 15 days ago·verify at source

Get an email when Red Hat publishes the next one.

See Red Hat's last 90 days of advisories first. Then choose one product with live alerts free for life, or a free month of real-time alerts on everything with the severity, the fixed version and the vendor's link (card needed, then US$15/month; we email you before the first charge).

Alert me about Red Hat

More Red Hat Linux advisories

All Red Hat Linux advisories

iPhone and Android apps · New on the App Store

Monitor future Red Hat Linux CVEs from your phone.

Choose a whole vendor or a precise platform, then receive matching security advisories by phone notification, email, or both. Coverage follows 34 official vendor sources and 160+ reviewed platform categories.

Download on the App StoreGet CVE alerts on AndroidSee app features

Discussion(0)

No comments yet. Share field notes, upgrade gotchas, or questions — verify against the vendor advisory before acting on community advice.

Sign in to join the discussion.