Look up another CVE · open CVE-2026-64047 in the interactive tracker
CVE-2026-64047
net: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/tls. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64047 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When an sk_msg scatterlist ring wraps (sg.end < sg.start), tls_push_record() chains the tail portion of the ring to the head using sg_chain(). An extra entry in the sg array is reserved for this: struct sk_msg_sg { [...] /* The extra two elements: * 1) used for chaining the front and sections when the list becomes * partitioned (e.g. end < start). The crypto APIs require the * chaining; * 2) to chain tailer SG entries after the message. */ struct scatterlist data[MAX_MSG_FRAGS + 2]; The current code uses MAX_SKB_FRAGS + 1 as the ring size: sg_chain(&msg_pl->sg.data[msg_pl->sg.start], MAX_SKB_FRAGS - msg_pl->sg.start + 1, msg_pl->sg.data); This places the chain pointer at sg_chain(data[start], (MAX_SKB_FRAGS - msg_start + 1) .. = &data[start] + (MAX_SKB_FRAGS - msg_start + 1) - 1 = data[start + (MAX_SKB_FRAGS - start + 1) - 1] = data[MAX_SKB_FRAGS] instead of the true last entry. This is likely due to a "race" of the commit under Fixes landing close to commit 031097d9e079 ("bpf: sk_msg, zap ingress queue on psock down") Convert to ARRAY_SIZE and drop the data[start] / - start (as suggested by Sabrina).
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/tls/tls_sw.c
- What this is
- NETWORKING [TLS]MAINTAINERS section matched on net/tls/ · netdev@vger.kernel.org · Maintained
- Kernel module
- tls
Check it on the machine
grep -w CONFIG_TLS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w tlsPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_TLS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-19 (3 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.51%, higher than 42.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/tls
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.5 | 5.10.258 | 73963a375885 |
| 5.5 | 5.15.209 | 47110c3a9ac2 |
| 5.5 | 6.1.175 | 84158c299715 |
| 5.5 | 6.6.142 | 131ef12057d9 |
| 5.5 | 6.12.92 | 66339b71f105 |
| 5.5 | 6.18.34 | eca989eab4b2 |
| 5.5 | 7.0.11 | 2fb0dc7e0099 |
| 5.5 | 7.1 | 285943c6e7ca |
| 5.4.14 | 0 | 0 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The flaw is in kernel TLS (kTLS) software transmit encryption triggered when a TLS socket sends records; remote peers on established TLS connections drive this TX path through normal network I/O.
- AC:LAttack complexity, low
- An attacker who controls connection traffic can reliably create the wrapped sk_msg ring state via BPF sockmap SK_MSG verdict helpers (push/pop/redirect) and then trigger record push on demand.
- PR:NPrivileges required, none
- Exploitation requires no privileges on the target host beyond being a network peer on a kTLS socket with sockmap BPF already configured by the service; attacker capabilities are not needed on the victim system.
- UI:NUser interaction, none
- Triggering requires only automated server-side TLS transmit activity in response to network input, with no victim user action.
- S:UScope, unchanged
- Impact is kernel memory corruption and potential privilege escalation within the same kernel/host security boundary, not a cross-VM or sandbox escape by itself.
- C:HConfidentiality impact, high
- Corrupting an active scatterlist entry causes the AEAD crypto path to follow an incorrect chain, enabling out-of-bounds kernel memory reads beyond intended plaintext buffers.
- I:HIntegrity impact, high
- The malformed scatterlist passed to crypto_aead_encrypt() can direct encryption I/O to wrong memory regions, providing an out-of-bounds write primitive exploitable for control-flow hijacking.
- A:HAvailability impact, high
- Scatterlist corruption in the kernel crypto TX path can cause kernel oopses, panics, or fatal BUG conditions when invalid chain entries or page pointers are dereferenced.