CVE-2026-89783 (CVSS 9.8)

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full The depth check in xfrm6_input_addr() is off by one: if (1 + sp->len == XFRM_MAX_DEPTH) goto drop; ... sp->xvec[sp->len++] = x; xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode receive path re-enters IPv6 input via xfrm_trans_reinject() with that secpath preserved. If the inner packet carries a destination-options HAO option or a type-2 routing header, xfrm6_input_addr() is called with sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS flags it and panics under panic_on_warn. Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also restores one chain level the old check rejected at sp->len == 5. UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10 index 6 is out of range for type 'xfrm_state *[6]'

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0021

Probability of exploitation

0.11%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other References

https://git.kernel.org/stable/c/0f679e0523ddfff3fb554336ceb874b0e51e9cd3 https://git.kernel.org/stable/c/48996649222e95008cdb98cd58579e3fc8e5ee06 https://git.kernel.org/stable/c/5d9e3bf34fec9a5d237e4b7cef4a707bc2e091bc https://git.kernel.org/stable/c/5f35a29a5eed3d80befd32050843ac88dea3d61a https://git.kernel.org/stable/c/68e8737fe8e72f085c608cff322b3d2de8340af1 https://git.kernel.org/stable/c/8fe2c53fb81f5ad5be43af2ad09583f7c78b4b77 https://git.kernel.org/stable/c/91fc387f63c00ddfb5221127a17bac97549a8343 https://git.kernel.org/stable/c/bdcda866c89f9a8b1acdabf02d26cde9fbe501d8

Frequently Asked Questions

What is CVE-2026-89783? +

In the Linux kernel, the following vulnerability has been resolved: xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full The depth check in xfrm6_input_addr() is off by one: if (1 + sp->len == XFRM_MAX_DEPTH) goto drop; ... sp->xvec[sp->len++] = x; xfrm_input() can leave sp->len == XFRM_MAX_DEPTH, and the transport-mode receive path re-enters IPv6 input via xfrm_trans_reinject() with that secpath preserved. If the inner packet carries a destination-options HAO option or a type-2 routing header, xfrm6_input_addr() is called with sp->len == XFRM_MAX_DEPTH; the check (1 + 6 == 6) is false, so sp->xvec[sp->len++] writes one slot past the 6-element xvec[]. The write stays within the sec_path allocation (invisible to KASAN); UBSAN_BOUNDS flags it and panics under panic_on_warn. Use "sp->len >= XFRM_MAX_DEPTH", matching xfrm_input(). This also restores one chain level the old check rejected at sp->len == 5. UBSAN: array-index-out-of-bounds in net/ipv6/xfrm6_input.c:309:10 index 6 is out of range for type 'xfrm_state *[6]' It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-89783? +

CVE-2026-89783 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0021, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-89783? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

CVE-2026-89783