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CVE-2026-89542— SUNRPC: harden gss_krb5_unwrap_v2 against short tokens

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于gss_krb5_unwrap_v2未校验令牌长度和缓冲区边界，可能导致越界读取、整数下溢、除零及内存损坏，进而造成拒绝服务。

CVSS 9.8 · Critical EPSS 0.52% · P43

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux de9c17eb4a912c9028f7b470eb80815144883b26< 299d281c7225ded15b28cb861a98d818d82787fc affected
de9c17eb4a912c9028f7b470eb80815144883b26< 84ddbc8d084c0251d534f14f5d1a7da05be56404 affected
de9c17eb4a912c9028f7b470eb80815144883b26< 075d7cfc4df8c54cb202ba8b28420370c03ba9b6 affected
de9c17eb4a912c9028f7b470eb80815144883b26< f2591660e0eb263c9415bf0d0bb1b111e62df7a4 affected
de9c17eb4a912c9028f7b470eb80815144883b26< dddcb0f4b7e27fac16a78ea9a1c8ec2e8a241087 affected
de9c17eb4a912c9028f7b470eb80815144883b26< 806584a4b67a7233870c33e5b8f872e76dd02988 affected
de9c17eb4a912c9028f7b470eb80815144883b26< a7894e10572d53eb10109b8d07459cc8d3435811 affected
de9c17eb4a912c9028f7b470eb80815144883b26< 6959297aaa9572783d620a226d73c3fb94494888 affected
… +10 more rows
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I. Basic Information for CVE-2026-89542

Vulnerability Information
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Vulnerability Title
SUNRPC: harden gss_krb5_unwrap_v2 against short tokens
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: harden gss_krb5_unwrap_v2 against short tokens gss_krb5_unwrap_v2() reads the EC and RRC header fields at ptr+4 and ptr+6 before validating that the token is at least GSS_KRB5_TOK_HDR_LEN (16) bytes long, and its rotate_left() helper passes buf->len - base to xdr_buf_subsegment() without verifying that base <= buf->len. When a caller hands in a sub-16-byte token, or a token whose declared len leaves base past the end of the buffer, three distinct failures follow: gss_krb5_unwrap_v2(offset, len, buf) ptr = buf->head[0].iov_base + offset ec = *(ptr + 4) /* OOB read on short head */ rrc = *(ptr + 6) /* OOB read on short head */ rotate_left(offset + 16, buf, rrc) xdr_buf_subsegment(buf, &subbuf, base, buf->len - base) /* u32 wrap when base > len */ _rotate_left(&subbuf, shift) shift %= buf->len /* divide-by-zero when base == len */ After decryption, the cleanup arithmetic has the same shape: movelen = min_t(unsigned int, buf->head[0].iov_len, len); movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip; BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen > buf->head[0].iov_len); The BUG_ON re-adds the value just subtracted, so it reduces to min(A, B) > A and is permanently false; it cannot catch the unsigned underflow of movelen, which then drives a ~UINT_MAX-byte memmove(). Add four defense-in-depth guards inside the unwrap core so it is safe regardless of what its callers validate: - reject tokens with len - offset < GSS_KRB5_TOK_HDR_LEN before touching ptr+4/ptr+6; - bail from rotate_left() when buf->len <= base, covering both the underflow and zero-length cases; - return early from _rotate_left() when buf->len is zero, so the shift %= buf->len modulo cannot fault; - replace the dead BUG_ON with a live check that returns GSS_S_DEFECTIVE_TOKEN before the movelen subtraction.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于gss_krb5_unwrap_v2未校验令牌长度和缓冲区边界，可能导致越界读取、整数下溢、除零及内存损坏，进而造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux de9c17eb4a912c9028f7b470eb80815144883b26 ~ 299d281c7225ded15b28cb861a98d818d82787fc -
Linux Linux 2.6.35 -

II. Public POCs for CVE-2026-89542

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III. Intelligence Information for CVE-2026-89542

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Patches & Fixes for CVE-2026-89542 (8)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown
CVE-2026-89712 9.8 CRITICAL NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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