VulnerabilityPublished 29 Dec 2024Updated 31 Dec 2024

CVE-2024-56738: GNU GRUB2 · Timing Side Channel

Affects GNU GRUB2Source CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Debiandebian/grub2`pkg:deb/debian/grub2`Other threats	Affected =2.00	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Monitor official GNU GRUB2 channels and repositories for patches addressing CVE-2024-56738 and apply updates promptly once available.
Until patches are released, consider implementing additional boot security controls such as Trusted Platform Module (TPM)-based measurements and secure boot configurations to reduce exposure.
Restrict network access to systems during the boot process where feasible to limit attacker ability to measure timing discrepancies remotely.
Employ system and network monitoring to detect anomalous timing analysis attempts or unusual bootloader interactions.
For environments using full disk encryption or sensitive bootloader configurations, consider layered encryption or multi-factor authentication mechanisms to mitigate key exposure risks.
Conduct regular security audits of bootloader configurations and cryptographic implementations to identify and remediate potential side-channel vulnerabilities.
Educate system administrators about the risks of timing side-channel attacks and the importance of timely patching and secure boot practices.

Description

GNU GRUB (aka GRUB2) through 2.12 does not use a constant-time algorithm for grub_crypto_memcmp and thus allows side-channel attacks.

Impact

The primary impact of CVE-2024-56738 is the potential leakage of sensitive cryptographic information during the boot process, which could compromise system confidentiality. Attackers exploiting this vulnerability might recover secrets such as encryption keys or passwords used by GRUB2, potentially enabling further attacks like unauthorized disk decryption or boot integrity bypass. Although the vulnerability does not affect system integrity or availability directly, the exposure of bootloader secrets can weaken the overall security posture of affected systems. Organizations with high-security requirements, such as those using full disk encryption or secure boot mechanisms relying on GRUB2, are at increased risk. The vulnerability could facilitate advanced persistent threats or espionage activities targeting critical infrastructure. Since exploitation requires no privileges or user interaction and can be performed remotely, the attack surface is broad. However, the absence of known exploits and the medium CVSS score suggest that immediate widespread impact is limited but should not be underestimated in sensitive environments.

CWE-208Observable Timing Discrepancy (opens in a new tab)
Base weakness
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Cross-Domain Search Timing (opens in a new tab)
Application Fingerprinting (opens in a new tab)
System Footprinting (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

savannah.gnu.org/bugs/?66603 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Feb 2026, 23:59 UTC

WeaknessesCWE-208

Technical details

References

Community reviews

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