CVE-2021-1931Public exploit

Bootloader code execution via undersized fastboot receive buffer

Published Jul 13, 2021 · Updated Aug 3, 2024

Buffer overflow in Qualcomm Snapdragon fastboot firmware allows local users with high privileges to execute code via oversized commands. FastbootMain.c allocates a 1 MB receive buffer even though the USB transfer path accepts commands as large as 16 MB, so oversized command data overwrites bootloader memory. The device must be placed in USB-accessible fastboot mode; successful exploitation can modify the loaded bootloader, bypass signature checks, or crash it until a forced reboot.

CVSS severity6.7
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in Qualcomm Snapdragon fastboot firmware allows local users with high privileges to execute code via oversized commands. FastbootMain.c allocates a 1 MB receive buffer even though the USB transfer path accepts commands as large as 16 MB, so oversized command data overwrites bootloader memory. The device must be placed in USB-accessible fastboot mode; successful exploitation can modify the loaded bootloader, bypass signature checks, or crash it until a forced reboot.

The record

CVE
CVE-2021-1931
Published
Jul 13, 2021
Updated
Aug 3, 2024
Vendor
Qualcomm
Product
Snapdragon
Classifications
CWE-120, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=AQT1000, AR8031, AR8035, CSRA6620, CSRA6640, CSRB31024, FSM10055, FSM10056, QCA6174A, QCA6310, QCA6320, QCA6335, QCA6390, QCA6391, QCA6420, QCA6421, QCA6426, QCA6430, QCA6431, QCA6436, QCA6564, QCA6564A, QCA6564AU, QCA6574, QCA6574A, QCA6574AU, QCA6584AU, QCA6595AU, QCA6696, QCA8337, QCA9377, QCM2290, QCM4290, QCM6125, QCS2290, QCS405, QCS410, QCS4290, QCS603, QCS605, QCS610, QCS6125, SA415M, SA6145P, SA6150P, SA6155, SA6155P, SA8145P, SA8150P, SA8155, SA8155P, SA8195P, SD 636, SD 675, SD 8C, SD 8CX, SD460, SD480, SD660, SD662, SD665, SD670, SD675, SD678, SD690 5G, SD710, SD720G, SD730, SD750G, SD765, SD765G, SD768G, SD778G, SD780G, SD835, SD845, SD855, SD865 5G, SD870, SD888, SD888 5G, SDM630, SDM830, SDX24, SDX50M, SDX55, SDX55M, SDXR1, SDXR2 5G, SM4125, SM6250, SM6250P, SM7250P, SM7315, SM7325P, WCD9326, WCD9335, WCD9340, WCD9341, WCD9370, WCD9371, WCD9375, WCD9380, WCD9385, WCN3910, WCN3950, WCN3980, WCN3988, WCN3990, WCN3991, WCN3998, WCN3999, WCN6740, WCN6750, WCN6850, WCN6851, WCN6856, ...[truncated*]

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Qualcomm · Snapdragonversion=AQT1000, AR8031, AR8035, CSRA6620, CSRA6640, CSRB31024, FSM10055, FSM10056, QCA6174A, QCA6310, QCA6320, QCA6335, QCA6390, QCA6391, QCA6420, QCA6421, QCA6426, QCA6430, QCA6431, QCA6436, QCA6564, QCA6564A, QCA6564AU, QCA6574, QCA6574A, QCA6574AU, QCA6584AU, QCA6595AU, QCA6696, QCA8337, QCA9377, QCM2290, QCM4290, QCM6125, QCS2290, QCS405, QCS410, QCS4290, QCS603, QCS605, QCS610, QCS6125, SA415M, SA6145P, SA6150P, SA6155, SA6155P, SA8145P, SA8150P, SA8155, SA8155P, SA8195P, SD 636, SD 675, SD 8C, SD 8CX, SD460, SD480, SD660, SD662, SD665, SD670, SD675, SD678, SD690 5G, SD710, SD720G, SD730, SD750G, SD765, SD765G, SD768G, SD778G, SD780G, SD835, SD845, SD855, SD865 5G, SD870, SD888, SD888 5G, SDM630, SDM830, SDX24, SDX50M, SDX55, SDX55M, SDXR1, SDXR2 5G, SM4125, SM6250, SM6250P, SM7250P, SM7315, SM7325P, WCD9326, WCD9335, WCD9340, WCD9341, WCD9370, WCD9371, WCD9375, WCD9380, WCD9385, WCN3910, WCN3950, WCN3980, WCN3988, WCN3990, WCN3991, WCN3998, WCN3999, WCN6740, WCN6750, WCN6850, WCN6851, WCN6856, ...[truncated*]

Published CVSS scores

6.7Qualcomm, Inc.CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

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

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1068Exploitation for Privilege Escalation

Public exploit references

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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