CVE-2026-74577

Local heap-byte disclosure via uninitialized rtm_tos

Published Aug 15, 2026 · Updated Aug 15, 2026

Information disclosure in the Linux kernel allows local users to read one byte of uninitialized heap memory through an MPLS route query. The mpls_getroute() function builds an RTM_NEWROUTE reply in a non-zeroed skb and leaves the rtm_tos byte unset before recvmsg() copies the header to user space. Reachability requires an existing MPLS route and a non-RTM_F_FIB_MATCH RTM_GETROUTE request for its label; each response exposes exactly one stale heap byte.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Linux kernel allows local users to read one byte of uninitialized heap memory through an MPLS route query. The mpls_getroute() function builds an RTM_NEWROUTE reply in a non-zeroed skb and leaves the rtm_tos byte unset before recvmsg() copies the header to user space. Reachability requires an existing MPLS route and a non-RTM_F_FIB_MATCH RTM_GETROUTE request for its label; each response exposes exactly one stale heap byte.

The record

CVE
CVE-2026-74577
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <1fea5ff0eb4aa7e951bb3d380248566c473aa377
  2. Affected versionversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <295dd295e2137e10e9a5b1891d97e0f08de76f03
  3. Affected versionversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <2dc2fffc704a4365cae1aae078ba62223aaeff93
  4. Affected versionversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <95651461cf77cc6590fa08c87667717e5dcfa55d
  5. Affected versionversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <a5cdd2407dd890f741f59b8367e4c6c101cce154
  6. Affected versionversion=4.13

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=397fc9e5cefee0c33b86811fbddb0decb7288c52 <1fea5ff0eb4aa7e951bb3d380248566c473aa377; version=397fc9e5cefee0c33b86811fbddb0decb7288c52 <295dd295e2137e10e9a5b1891d97e0f08de76f03; version=397fc9e5cefee0c33b86811fbddb0decb7288c52 <2dc2fffc704a4365cae1aae078ba62223aaeff93; version=397fc9e5cefee0c33b86811fbddb0decb7288c52 <95651461cf77cc6590fa08c87667717e5dcfa55d; version=397fc9e5cefee0c33b86811fbddb0decb7288c52 <a5cdd2407dd890f741f59b8367e4c6c101cce154; version=4.13

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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