CVE-2026-74478: um: vector: fix use-after-free in vector_mmsg_rx()
Vulnerability summary
CVE-2026-74478 is a critical (CVSS 9.8) vulnerability in linux. EPSS estimates a 0.86% chance of exploitation in the next 30 days, higher than 58.7% of scored vulnerabilities.
Severe, CVSS 9.8 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 05-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 10 · Related 7Timeline
- 15-08-2026PublishedVulnerability first disclosed.
- 19-08-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: um: vector: fix use-after-free in vector_mmsg_rx() When vector_mmsg_rx() discards a packet whose overlay header fails verify_header(), it frees the skb and continues the loop: if (header_check < 0) { dev_kfree_skb_irq(skb); vp->estats.rx_encaps_errors++; continue; } The normal and short-packet paths fall through to the bottom of the loop body, which clears the consumed slot and advances the cursors: (*skbuff_vector) = NULL; mmsg_vector++; skbuff_vector++; The verify_header() < 0 path skips that via continue, so the freed skb is left in skbuff_vector[] and the cursors do not advance. The next iteration reads the same slot, gets the freed skb, and frees it again, producing a refcount underflow / use-after-free in the RX path. Discard the slot the same way the other paths do before continuing. Only transports whose verify_header() can return negative are affected: GRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not), so any peer on such a transport can trigger it without authentication.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.86%
Chance of exploitation in the next 30 days
Percentile
59%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.86% on 06-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu165 products
- linuxAll versions (No fix recorded) | < 5.15.0-198.208 | < 7.0.0-42.42
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1117.124 | < 7.0.0-1016.17
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Debian2 products
- linux< 6.1.187-1 | < 6.12.105-1 | < 7.1.8-1
- linux-6.12< 6.12.107-1~deb12u1
Linux1 product
- linux≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 967c779c9853d2a1cc9cd8e61d300250c348f3d9 | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < a7bc015bb798c525e7a82dd14225c6aeb994274b | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 7dc9781e320d664c9bdd50003c9acfddf363d1e1 | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 4b9601595e8b6b5d18878cac0aeabc687d241111 | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 67d58ab4f2ccf7145f3da07e025735a09c79de1b | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 180ff4c81faf01ec4e06082c9daa7c40518ead89 | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < 804b681002ead233abf49a3efd681f5468a835f9 | ≥ 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb, < af421e9aed3920c7ac88c24daa48606c7112feca | 4.17
3 vendors · 168 products
