CVE-2015-2688Network attack vector

Remote relay crash via empty buffer chunk

Published Jan 24, 2020 · Updated Aug 6, 2024

Buffer-handling failure in Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 allows remote attackers to crash relays. When the requested byte count exactly equals a source chunk's data length, buf_pullup advances the data pointer to the allocation boundary but leaves an empty chunk that violates a buffer invariant. A crafted packet must reach a relay when its receive buffer has this layout; successful exploitation triggers an assertion and exits the daemon.

CVSS severity7.5
High
EPSS probability2.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer-handling failure in Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 allows remote attackers to crash relays. When the requested byte count exactly equals a source chunk's data length, buf_pullup advances the data pointer to the allocation boundary but leaves an empty chunk that violates a buffer invariant. A crafted packet must reach a relay when its receive buffer has this layout; successful exploitation triggers an assertion and exits the daemon.

The record

CVE
CVE-2015-2688
Published
Jan 24, 2020
Updated
Aug 6, 2024
Vendor
The Tor Project
Product
Tor
Classifications
CWE-755, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 24, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 6, 2024Record 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=0.2.5.x before 0.2.5.11
  2. Affected versionversion=before 0.2.4.26

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Tor Project · Torversion=0.2.5.x before 0.2.5.11; version=before 0.2.4.26

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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