9.8

CVE-2026-89778: isofs: fix out-of-bounds page array access on empty zisofs block

Received
AliasesUBUNTU-CVE-2026-89778DEBIAN-CVE-2026-89778
Published 16-09-2026Last modified 19-10-2026

Vulnerability summary

CVE-2026-89778 is a critical (CVSS 9.8) vulnerability in linux. EPSS estimates a 0.70% chance of exploitation in the next 30 days, higher than 53.1% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.8 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.70%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 11 · Related 11
OPENSUSE-SU-2026:11880-1OPENSUSE-SU-2026:22167-1SUSE-SU-2026:24371-1SUSE-SU-2026:24379-1SUSE-SU-2026:24386-1SUSE-SU-2026:24422-1

Timeline

  1. 16-09-2026
    PublishedVulnerability first disclosed.
  2. 19-10-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: isofs: fix out-of-bounds page array access on empty zisofs block zisofs_uncompress_block()'s empty-block fast path returns pcount << PAGE_SHIFT, ignoring the incoming poffset, unlike the decompression path which returns bytes produced relative to poffset. zisofs_fill_pages() uses that return to advance its page cursor, so when the zisofs block size is below PAGE_SIZE and a sub-page block leaves poffset partway into a page, a following empty block over-counts and advances pages[] one element past its end, after which "if (poffset && *pages)" reads pages[1] out of bounds. rock.c only rejects a block-size shift > 17, so a crafted "ZF" Rock Ridge record can set it below PAGE_SHIFT; the bug is reached by an ordinary read() of a compressed file on such a mounted ISO9660 image. Return the byte count relative to poffset and zero only [poffset, PAGE_SIZE) of the first page, matching the decompression path. The page-aligned case (poffset == 0) is unaffected. BUG: KASAN: slab-out-of-bounds in zisofs_read_folio (fs/isofs/compress.c:290) Read of size 8 at addr ffff88800f5eac48 by task exploit/142 zisofs_read_folio (fs/isofs/compress.c:290) read_pages (mm/readahead.c:184) ... filemap_read (mm/filemap.c:2814) vfs_read (fs/read_write.c:574) __x64_sys_pread64 (fs/read_write.c:769) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) The buggy address is located 0 bytes to the right of the allocated 8-byte region in the kmalloc-8 cache

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.70%

Chance of exploitation in the next 30 days

Percentile

53%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 0.74% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu169 products
  • linuxAll versions (No fix recorded)
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian2 products
  • linuxAll versions (No fix recorded) | < 6.1.190-1 | < 6.12.111-1 | < 7.2.6-1
  • linux-6.12< 6.12.111-1~deb12u1
Linux1 product
  • linux≥ 59bc055211b8d266ab6089158058bf8268e02006, < 8b994ac5778a725982fd6a8a3afcaa068d4a93e3 | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < 85904076cece72ee3194646ad7ac8e6659d999aa | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < f03425dcbe04aec3c27b9917e97d7d23a2908dda | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < cd616aa0449a772a6956abf03358f0ff31720580 | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < 9c6eace8d07e90f038c89eb3b756d65a7e259d48 | ≥ 59bc055211b8d266ab6089158058bf8268e02006, < 68d4d3e78150c7ed7d1195af63ad1e6ace30c661 | 2.6.33

3 vendors · 172 products

References

12 links
Show all 12 references